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Krell Solo 575 XD mono amplifier, $15,000 for perfect sound

Dale Davies |
Krell’s XD upgrade for the iBias amplifiers takes an already great sounding amplifier and raises its performance to the next level.

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Krell’s history is rich with breakthrough Class A amplifiers that have helped build the Krell legacy of offering the best sounding amplifiers available. Power supply technology has always been an important contributor to the Krell sound. The power supplies of our Krell iBias Class A amplifiers have been optimized for use with the iBias circuit. Depending on the model, up to four toroidal transformers feed amplifier modules that include the audio circuitry, rectifier, and power supply filtering mounted to an individual heat sink.

This design shortens the electrical path from the power supply to the output transistors, reducing the overall impedance and allowing the circuit to respond faster and control the speakers even better and more accurately. Unlike traditional Class A amplifiers, iBias Class A amps have a compact design that allows rack mounting, making them ideal for custom installation as well as traditional audiophile systems. This convenient form factor is made possible through thermostatically controlled ventilation fans.

The fans used are specifically chosen for quiet operation, and operate at the speed required to maintain the ideal internal temperature. They run only during periods of peak energy demand when the music is at its loudest so they are inaudible in normal use. The new iBias circuitry is built on a foundation of core Krell circuit technologies. All signal gain is realized in the current domain using proprietary multiple output current mirrors with extraordinary open loop linearity. Each amplifier channel uses all discrete components. There are no generic integrated circuits or op amps used anywhere.

Gain is distributed among several stages, allowing each to have a large linear operating area. Krell amplifiers are fully direct coupled, with no capacitors in the audio signal path. This design gives the Krell amplifiers lower internal impedance, which allows firmer, more precise control of your speakers. For more than $15,000 you get 575 W RMS at 8 Ω or 900 W RMS at 4 Ω of perfect sound. This is an amplifier you definitively must hear.

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